Good One Bruce,

I hope that clears the air a bit. I think you meant "Mythbusters" tradition rather than "Ghostbusters" tradition-- I'd hate to see you covered in marshmallow. 

pqe

This months DCC

As usual, I learned something I did not understand before.  Many thanks, Bruce.

...don

Ops Mode Programming Risks

There is a risk with Ops Mode programming that I think should be pointed out. It is probably specific to Digitrax. When you press the button to go into programming mode on the throttle it cycles through the different programming modes, one of which is Ops mode (shown as Po on the throttle). First you need to be certain which throttle is the active one before going into Programming mode so that you are programming the correct one, second you need to be sure you are in Ops mode. This usually isn't a problem the first time; let me give you an example. I want to change the momentum settings of a particular locomotive, I dial up the address, go into Programming mode, cycling through the modes to Ops Mode, I then make the change, exit and give it a try. I find that I want to give it a little more momentum, so I hit the programming button again, but I accidentally hold the button down too long and it picks it up twice, so instead of being in Ops mode I am now in direct mode, I make my change, hit enter and every loco on the tracks has been changed!

I have done this more than once! Yes it is stupid operator error, but those annoying little buttons on Digitrax throttles do this all the time and I find that I can get so involved in observing the change that I forget to double check the throttle display and Boom! you hear that Beep that tells you that you just reprogrammed everything!

Now I try to take the other locomotives off before I do Ops Mode programming, or park them somewhere on a dead track. I find it happens most often when adjusting sounds, I am making multiple changes and listening for the change in sound, after doing it a number of times, and I almost have gotten it just about right, I decide one more tweak will be perfect and forget to double check the throttle and Boom!, now I have to reprogram all the locomotives!

This is one of the best things with JMRI, if you mess up you just have to call up the locomotive in JMRI and you can reprogram it back to they way you had it. Of course the best thing would be to use JMRI even when doing Ops Mode programming, but that means setting up the computer and my PR3, so I don't always do it.

Brent

Calgary

Brent, I don't understand how

Brent, I don't understand how you are programming your whole layout in direct mode? If you have an isolated track for your direct mode programming, this shouldn't be an issue.

The Gremlin within.

Don't feel bad Brent as we have a club gremlin that is policed because he made that very same mistake and reprogrammed every loco address on the layout. Kind of scary when you see more than a dozen trains take off at the same time.

This is why I prefer to have a program track separated from the layout entirely. I know it adds risk to handling the locos, but that is my preference.

Brent

What system are you using, a DB150, or a DCS? I expect a DB150.

If, indeed, you are using a DB, then this is a DB issue, not a Digitrax issue:

As I explained, the DB150 USES THE ENTIRE LAYOUT AS A PROGRAMMING TRACK.

The scenario you explained is EXACTLY what I'd expect.

You are NOT Programming on the Main - you are using the layout as a programming track - big difference!

The Auto-Switch mentioned in the article will fix this FOREVER! Not bad for about $25. No more policing folks like John mentioned.

POOF - one more myth marshmallowed! Now a baker's dozen.

DB150

Yes, I have a DB150, but the point that I am trying to get to is that I would use programming on the main so that I can see and hear the results of the changes, to do that I have the loco running around the layout when I make the changes. I do have a separate programming track for changing addresses etc, but I usually do that using JMRI. If I am programing on the main I have the loco running and am adjusting things like the chuff timing, or various sounds or speed tables, and it is much easier to do that on the layout with the loco running around.The danger that I am pointing out is that with Digitrax is to inadvertently having the system switch from Po (programming on Main) to something like Pg (paged mode) mode without realizing it until you hit the enter key! It is due to those funky keys on the throttle that don't always work the way they should.

So there are risks to using programming on the main that you need to be aware of at least when using Digitrax throttles. If I bring out the computer and use JMRI then it is not an issue as it will stay in the correct mode, its only an issue with using the Digitrax throttle. And those keys are a whole nuther issue...

Brent

Sound unit precautions.

Bruce, Another great read. Thank you.

You mentioned the inrush from sound units and it has me wondering about our N scale freemo set up. There are times when we might have a dozen or even more sound units in one district upon start up or booster reset after a short. When you use the term cold start would that be referring to the first power up of the layout for the day? Are there any settings on the decoders or otherwise we might be able to use to help the boosters reset more reliably after a short. Maybe sound off until the user activates or something like that. We are adding circuit protection going forward, but if there are any recommended practices or settings I sure would like to share them with the group.

We have been running Digitrax with a Command station (no track connection) plus five booster districts and now will have those booster districts divided further with circuit protection.

Capacitors will hold a charge

a surprisingly long time, so the big rush mostly will happen on the first power up of the day. If the layout is reset within a few minutes, problems are unlikely. One option is to put the locos out one at a time with power running.

pqe

So if left on the layout over

So if left on the layout over night would it be beneficial to turn off the sound before powering the layout down? This way there would be no inrush when we power the layout up? Am I over thinking this ad is not really that big a deal?

Brent

AGAIN, I'll say it. This is NOT a DIGITRAX issue and it is NOT a Programming-on-the-main issue. It is an case of a user THINKING he is programming-on-the-main and actually turning the entire layout into a programming track.

As I said, there is nothing inherently dangerous with programming-on-the-main. The MYTH is that there is.

All of the Digitrax full fledged command stations (DCS series) do NOT have the problem. I asked the owners of Digitrax, almost a decade ago, to stop selling the DB150 as a system. I have NEVER recommended it to any customer or client. It is a booster with a VERY limited command station and no programming track. They continue to sell it because of its price point. Over the years DB150 owners exhibit the most buyers' remorse of any DCC system buyers I have encountered - mostly for the lack of a programming track, EXACTLY the issue here.

There is, however, a $25 fix for it, as I mentioned in the article and on this thread. Use a NCE Auto-Switch. But that $25 patch eats up all but $40 of the difference between the Super Empire Builder Xtra and the Super Chief Xtra. You get WAY more than your money's worth with the Super Chief series.

Inrush current

The Digitrax booster will not handle inrush current with grace. About 3 or 4 decoders on one booster and it won't start.

Cold start is something like 10 minutes shut down. The capacitors will bleed off and they will draw a large current when power is applied. No, there is no reason to turn the sound off. The capacitor needs to charge whether the sound is active or not.

I don't like unnecessary handing of the locos or track block switches. So, the SOLUTION is to use a PSx series circuit breaker and set the "weak booster" personality. That might as well be called the "Digitrax" personality. I've seen a Digitrax booster come to its knees with 3 sound decoders. Add a PSx and set the personality and it would come up smoothly with 16 sound decoders.

Makes sense.

Its like buying the Powercab and wondering why there is no separate program track. I would say to read the manual before you buy it, but some shop workers are sellers and will sell anything to anyone regardless of experience. This is unfortunate and can drive people away.

New to this

You answered many questions about this. Thanks!

Thanks Bruce,

for your thorough explanation on the Inrush issue.

Multimeter

I have the multimeter you show in your article. With my NCE Power Cab I measure 13.6 VAC and about the same with the NCE Power Pro 5 amp system at the local club. Couple members have the same meter and show close to the same. I also have three other of the same meter and they all agree quite close. Never tried them on any other system.

The power supplies for the systems show about the same DC voltage which I would expect.

Just wondering.

Rich

...

To truely see the voltage, you need an oscilloscope.

DCC Mythbusters

Bruce, thank you for this one.  Two of these myths have been rattling round in my planning and never really resolved until this column.  So, you get a "Fantastic" rating from me on this one.  Now, where do I send all these DC system parts I have for recycle again?

Clyde

Edmonton AB

Programming on the main is dangerous

I have a second hand Atlas commander. It doesn't allow programming on the main BUT...

In my experience you can destroy the unit when programming. If you follow the documentation and connect the programming track and the main to the proper terminals the unit will burn a circuit. It is absolutely necessary to install an "either or" switch. The unit must be hooked uo so that both circuits CANNOT be live at the same time. This is regardless of the fact that the two tracks are completely separate.

Just a heads up for folks who may buy one on E-Bay

DCC myths.

    It only takes 2 wires to power the layout. Ya right. look under mine!

  Earlier Lenz systems had broadcast programming. Manny times all the locos on the rails were programmed by someone just trying to consist something.

All decoders will run on any DCC system. Ya Right. Try running an older NCE decoder on a Lenz with Railcom dcc system. Yes you can configure railcom to work with some NCE decoders  but others will be lost. There  is no trade off here. Either enable railcom and change out the decoders or disable railcom and keep truckin.

        Pete

Multimeter

I am late to this issue of the ezine and this DCC article. Regarding the comments about multimeters, I share Rich's reaction because I, too, have an inexpensive unit similar to that shown and I, too, have experienced consistent voltage readings. Depending on which probes are on which rail I get readings of either 13.4 v or 14.3 v. And these readings are consistent around the layout, a doughnut of modest size (nominally 8' x 12') with fewer feeders than the number usually favored by conventional approach.

I have a Zephyr Extra. At one time when I was experiencing some difficulties with the command station, I wrote the following to Digitrax: "Checked voltage on track ... per your instructions (used Zephyr ground & DC setting) and found 7.05 v @ rail A and 6.68 v @ rail B. If I use AC setting on multimeter, I get 14.5 v." Digitrax responded that those voltages are okay. 

So, like Rich, I am puzzled by the notion that these multimeters are inaccurate and produce wide variations in readings.

Dante

Accuracy costs money

...

Until you take the time to look at the voltage with an Oscilloscope, you won't know the difference between the readings...

But for our purposes..........

A good multimeter set on the AC scale gives you a voltage to work with.   Take your base reading directly from the command station output,  ( in my case it's at 14.8V AC)  As you check voltage around the layout, your reading should stay fairly consistant and only vary 2 to 3 points on the scale.  If you find a section that varies by more than that, that is a potential trouble spot, ie bad feeder, loose rail joiner, switch points not making good contact ect.  I find that diagnosing electrical trouble spots, I have very good luck using my good old 12V test light!  If it lights up bright, I have good power transfer. If it's dim or out I have a trouble spot that needs repair.